Plant Health

Blueberries

Plant health problems have been increasing with the age of the plantings. Stem blight caused by Botryosphaeria dothidea is the number one blueberry plant killer beyond management errors. It is associated with drought, pine voles, pruning practices and stem borer mentioned below. The second disease to kill blueberry plants is root rot caused by Phytophthora cinnamonii. In recently cleared areas prioness root borer killed plants for 6 or 7 years but the problem went away as the planting matured. We have lost plants to stunt rickettsia but we have not observed any on-farm spread. Most seems to come from the nursery and with careful rouging we have gotten rid of it all. The plant pathologist in me is satisfied that rouging worked. The last problem that takes bushes out is one I have dubbed "fall over" where the bush gets big with a narrow crown and just falls over. In about two years it will sprout back. This has been a problem in Climax and Centurion.

As for ripe blueberries, anthracnose is the biggest problem in blueberries. The symptom of ripe rot in blueberries is that the berries just look dirty. The disease will show up after the berries are picked. For commercial sales it is a serious problem.

Mummy berry in blueberry has shown up but was not a major problem till 1991 when we lost about 40% to the disease. It was serious in 1992 and 1993. In 1994 a full mummy berry program of 3 sprays was used with little disease evident. A full 4-spray (Indar) program was the standard in 2001. We purchased a sprayer in 2000 for $3000 because I just could not get the job done with a handgun every year. We have had some problems with Botrytis in cool wet weather on the flowers. We did an application of benomyl initially as last mummy berry spray till it was canceled for lack of company support; Rovral was then used once they start to drop the corollas (bloom) if it is wet. If frost occurs it can become epidemic. This is, in essence, a fourth or fifth mummy berry spray. We also integrate our herbicide program so it supplements mummy berry control as indicated above.

Pro Gib [aid in berry set and especially when frost occurs] is tank mix it with fungicides for mummy berry control depending on the stage of bloom. We apply 200 ppm at stage &frac45; in 40 gallons of water/ac and another 200 ppm at stage &frac56; about 10 days later. We have also used it at 100 ppm 4 times per season. It depends upon the how fast bloom is occurring and the rain. It’s expensive, about $132/ac for the Gib treatments not counting the fungicide. Funginex was canceled due to lack of company willing support the label. We have used ProGib with Indar and it seems to work equally as well. We are now moving to Serenade, an organic fungicide, for mummy berry. We use an organic material, Dipel (BT), for fruit worm control too. I also ran a bloom delay experiment using Ethrel (ethapon) applied in early-November under what was pretty much optimum conditions for IR-4. It did not work.

The cranberry fruit worm in blueberry is the next problem we address. It is always a problem to know when to put the first application of insecticide. Scouting is difficult. Blueberries usually bloom for about 8 weeks (March 15 to May 15). On the average, two sprays are applied of Bacillus thuringensis (Dipel an organic product) with the last 2 mummy berry sprays. Two sprays just about do the job. These and ProGib sprays are done at night, too, for maximum effect.

The next blueberry problem is the obera stem borer. We don't spray for this problem. Everybody is sensitized to the problem and whenever you see girdling, stop what you are doing and break it out. The first flags of the borer will show up about the 15 th to 20th of June. Stem blight frequently comes in on borer-damaged stems. These damaged stems must be pruned out before the blight reaches the crown. As the planting ages and bushes are big it is easy to miss these shoots and this problem becomes more severe. Most problems are not found till pruning time when a major stem in the bush appears weak, it is cut out and the borer hole is discovered and you have to keep cutting back to get below it. This makes a major cut that may not sprout or sprouts very weakly because of insufficient light penetration. The stem blight fungus colonizes this stub and moves into the root crown and eventually kills the bush. Research by Dr. Culin and students at Clemson University showed that Lecuothoe and native azaleas supports obera as well as its predators. The students showed significant predation at The Happy Berry. In older plantings a replanting program is required associated with this problem.

As the planting aged blueberry maggot became a major problem. This worm shows up after the customer gets home puts the berries on the counter. They exit the berry and accumulate in the bottom of the bowl. The blueberry maggot lives in native blueberries and closely allied species in the surrounding woods. They are weak flyers so move slowly into a planting. These are controlled by using Spinosad, an organic insecticide in molasses bait. The bait is sprayed on the inside stems of the bushes of every third bush. The problem was cleaned up in two to three years. Yellow sticky traps are used to monitor for the adult flies. Bait application is started about 7 days after the first fly catch and continues till no more flies are caught in about 2-3 weeks. Once under control perimeter treatments are made around the farm to prevent reentry with no bait applied in the bush.

A major problem for us is robin (Turdus migratorius) management. We have found that one application of Mesurol timed exactly right will give us 6-to 8-week control. The key is to apply the Mesurol before the birds start feeding but as late as possible with regards to the presence of palatable berries to birds, usually about the 15 to 18th of June. Mesurol is gone because of cancellation. We have tried Scare eye balloons. They seem to work in a small trial area (about 6 yards). The cost of balloons and something to put them up on, when buying in volume, is about $350 per acre, not including labor. There is also a biorational compound under development called Rejexit. We now use a computer chip that mimics the distress call of the common robin. It turns itself on and off automatically. As long as there is not an equipment failure and we start it before a feeding is established, it seems to work for about 3-4 weeks. We supplement this with small windmills with reflective tape that works on the same basis as the scare eye balloons but they last longer. The reflective tape needs to be repaired each year and they seem to have bigger area of effect especially when moved into the area after starting up the computer chip. A third integrated measure is the use of Screech owls discussed below. The screech owls get young fledglings while still in the nest, keeping local robins down which act as scout birds for the migrating flocks near the end of summer.

Another major problem is voles. We have used Rozol. This is a very labor-intensive baiting effort. We have discontinued Rozol and installed Barn owl, Screech owl and Kestrel boxes. The percent occupancy for Screech owls is best. If we feel we must apply poison bait, we use zinc phosphide. It does not bioaccumulate but is much more hazardous to the applicator. The screech owls are small enough to get between the bushes and can sit in the bush waiting for the prey to show up. Although we initially used Fescue, the heaviest vole population was always in the dense fescue area. With close clipping in the summer the crab grass has taken over and more recently Bahia grass. Where these grasses are present the vole problem has gone a way. The Bahia grass is manageable with Round up and holds the soil together well to handle winter traffic. The seed heads do cause a mowing problem. We are trying other summer grasses.

Other plant health-related problems we have investigated in blueberries are: solutions for winter cover crops (rye) for erosion control [very competitive and slowed growth] and use of compost as a layer to organically control weeds, mummy berry, and root rot. Both compost and acid mulch are very expensive even if you get it free. It is very labor-intensive to get it in place. I believe it promotes shrews (a natural enemy of voles), and enables bushes to tolerate root rot better. Mulch does not seem to impact mummy berry, at least in 5 foot wide treated areas.

Blackberries

The Raspberry crown borer is number one cause of death if not managed in blackberries. In blackberries we used diazone, until it canceled, then we used Guthion till it was canceled in 2005 as crown drench in early September and in May for the raspberry crown borer. We have found the fall application when berries are not around to be adequate. We anticipate using Capture in the future.

We scout for Strawberry clipper and use-to-use Sevin XLR at night for it. We did not like the persistence of Sevin and it was hard on mite predators. We now use Malathion and Capture. The Choctaw variety has the most problem with Clipper and we base our control tactics based on scouting in the Choctaw. We anticipate the Prime Jim and Jan will also have the same problem as they bloom even earlier than choctaw.

In the Thorny varieties, especially Shawnee, Chickasaw and little in Choctaw and less in Kiowa and Chester double blossom is a very serious problem. We hand pruned it out and sprayed with Benlate till it was canceled. We now use copper, strobilurins, Rovral and Elevate. We delay the first application till the rosettes start to bloom. We continue spraying and hand pruning till harvest is complete. Immediately after harvest we prune out the floracane and stop spraying. During harvest we use Rovral.

The above spray program also limits Botrytis, which is a smaller problem on blackberries than Raspberries. Chester has the most problem with Botrytis. Its late bloom always seems to get at least some Botrytis.

Mites are significant especially on Choctaw and Chickasaw but if left unchecked will damage other varieties too. Savey applied once a year 30 days prior to harvest works well. Since the preharvest interval is 3 days this adds to the safety factor.

The most significant problem in Blackberries is the virus complex. In the most of the thornless varieties to date the exceptions being Chester, Arapaho and Navaho the virus complex results in death of the plant. In Navaho, raspberry bushy dwarf virus results in small knobby berries. In Triple Crown and Apache the floracanes are killed outright with virtually no harvest. Arapaho suffers a dieback and small knobby berries also. The importance of virus free plants and eradicating wild brambles for at least quarter mile can’t be overemphasized. The thorny varieties Shawnee, Kiowa, and Chickasaw although susceptible to the viruses seem tolerate it and still have acceptable quality berries.

Grapes

There are several diseases of muscadine grapes including rip rot, bitter rot, Macrophoma rot, angular leaf spot, powdery mildew and black rot. We use Serenade, Prophyte and BT, all organic products, for disease and insect control. Although you can produce muscadines without sprays, they are not as sweet and have a shorter shelf life. There are usually about 8 cover sprays. We scout for grape root borer emergence by looking for the pupa case sticking out of ½ to ¾ inch diameter mounds. We use Lorsban as a directed spray to the ground at grape root borer emergence. Weed control is either Round up or Rely applied as needed. For aphids, Jap and June beetle, stink bugs we use Malathion when scouting indicates a problem. For various leaf galls mulch the foliage in the fall of the year with a finishing mower. For the several foliage feeding worms and the grape berry moth we use BT.

Raspberries

Botrytis, Spur Blight and Phytophthora root rot are the major fungal diseases of raspberries. The purple raspberry, Royalty, is very susceptible to spur blight. It is also susceptible to virus. Heritage red raspberry over time builds up root rot problems. Botrytis requires weekly sprays. Mandarin and Dorman red are very susceptible to red-necked cane borer. Warm spells in the winter bring the plants out of dormancy and then suffer cold injury and cane blight. We are trying black raspberries. We are not optimistic about raspberries in general.

Elderberries

The elderberry is not normally eaten out of hand. It is processed. There is a Hemipteran like bug that feeds on the developing canes and especially the berries. When crushed this bug gives off a distinctive odor which obnoxious. This bug is picked right along with the berries. If not removed the odor persist in products made from the berries. Now that I have experienced the problem I can smell it in Commercial products such as Smucker Elderberry Jelly. A reasonable control is needed for this bug. Powdery mildew is a problem resulting in late season defoliation. At this point it does not seem to be commercially significant. There is a cane borer, although noted while pruning we do not know its significance yet. There is also Xylella species reported in Elderberries.